Boat propeller



June 14, 1966 D. w. BECK 3,

BOAT PROPELLER Filed Oct. 12, 1964 2 Sheets-Sheet 1 12: 2/a/ By June 14, 1966 D. w. BECK BOAT PROPELLER Filed Oct. 12, 1964 2 Sheets-Sheet 2 By 01m 5% i L] A Wow/5y United States Patent 3,255,826 BUAT PRUPELLER David W. Beck, Lakeweod, Califi, assignor to Aerolab Development Co., Monrovia, Calif. Filed (Pet. 12, 1964, Ser. No. 403,052 1 Claim. (Cl. 170-16012) The present invention relates in general to the art of boating and boat construction and more particularly relates to a new and novel foldable boat propeller.

Many sailboats mount engine-driven propellers which are used on various occasions such as, for example, when the wind is down and in case of emergency. Furthermore, with respect to racing boats, it has been a common practice for the operators of these boats to use their engines or motors in returning to port after a hard race. Although a number of different benefits or advantages are obtained from the use of thesev propellers, which makes their use desirable, they are nevertheless disadvantageous in the respect that they introduce the problem of 3,255,326 Patented June 14, 1956 expressly understood, however, that the drawings are for drag which has the effect, as will be recognized by those I skilled in this art, of materially slowing down a boat when they are not actually in use. Boat operators have attempted to resolve this problem in the past by detaching the propeller and keeping it on board until needed. However, this technique has not really resolved the situation but has merely had the effect of substituting one problem for another in that it is time-consuming and oftentimes difficult, if not impossible, to attach the propeller once again as, for example, in the case of high seas.

It is, therefore, an object of the present invention to provide a propeller whose blades will provide the smallest possible silhouette when they are not in use.

It is another object of the present invention to provide a propeller for boats that will result in minimum drag when not in use.

It is a further object of the present invention to provide a propeller whose blades will automatically unfold or fold, depending on whether or not it is in use.

The present invention attains the objects mentioned and, in so doing, overcomes the several disadvantages encountered among the propellers found in the prior art. More particularly, in accordance with the concept of the present invention, a propeller is provided whose blades are rotatably mounted so that they can fold or unfold. When the propeller is in operation, centrifugal forces cause the propeller blades to fully unfold orextend themselves. However, when the propeller is not in use, the drag of the water causes the extended blades to fold or close, a significant feature of the invention being that, when they close, they blend in such a manner with the shaft member on which they are mounted as to thereafter reduce the drag to a minimum. Stated differently, it is a feature of the invention that, when the propeller blades are closed, the blades and their mounting apparatus present a streamlined configuration of minimum cross-sectional area to the water to thereby greatly reduce the drag, as previously mentioned. Hence, with this kind of propeller, greater speeds can be attained by the boat and, furthermore, the aforesaid problem of attaching and detaching the propeller is avoided.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the the purpose of illustration and description only and are not intended as a definition of the limits of the invention.

FIGURE 1 is a front view of a propeller according to the present invention as it is mounted on the rear of a boat and shows the propeller blades fully extended;

FIGURE 1(a) shows a side view of the propeller taken in the direction of arrows 41-11 in FIG. 1;

FIGURE 2 is a side view of the same propeller and shows the propeller blades in a partially closed position;

FIGURE 2(a) is an end view of the propeller shown in FIG. 2 and is taken in the direction of arrows 2a2a therein;

FIGURE 3 presents a side view of the propeller with its blades fully closed;

FIGURE 3(a) is also a side view of the propeller with its blades fully closed but with the propeller as it is shown in FIG. 3 turned through an angle of FIGURE 4 is a side view of the propeller in crosssection that is taken in the direction of arrows 44 in FIG. 3;

FIGURE 4(a) is an end view, in cross-section, of the propeller taken in the direction of arrows la-4a in FIG. 4; and

FIGURE 4(b) is also a side view of the propeller in cross-section but taken in the direction of arrows lb4b in FIG. 4.

For a consideration of the invention in detail, reference is now made to the drawings wherein like or similar parts or elements are given like or similar designations throughout the several figures. Referring first to FIGS. 1 and 1(a), the embodiment is shown to include a pair of propeller blades 10 and 11 mounted by means of a bolt 12 on an elongated hub member 13 which couples the propeller blades to the driveshaft (not shown) of the boats motor. The rear of a boat on which the propeller is mounted is shown in FIG. 1 and is designated 14 therein. Propeller blades 10 and 11 are mounted to pivot or turn around bolt 12 and, to properly permit this rotation, hub member 13 has a recess in its rear end into which the ends of the blades are sandwiched. The walls of this recess are designated 13a and 13b and the mounting ears of the blades fitted therebetween are designated 10a and 11a, the bolt 12 binding these parts together extending through holes in these parts that are aligned to form a channel for the bolt.

As is shown in .FIGS. 1 and 1(a), blades 10 and 11 are fully extended in a direction that is perpendicular to hub member 13, which is a condition that exists when the propeller is in actual use or operation. More specifically, when the propeller is put into use, the high speed of rotation of member 13 about its axis produces centrifugal forces which act upon the blades and, since these blades are mounted to pivot on bolt 12, the centrifugal forces cause them to open up until they become fully extended as shown. Thus, because of the weight of the blades and the distribution thereof, and because of the high speed of rotation of the hub and, therefore, of the blades, the centrifugal forces produced are of sufiicient magnitude to overcome the drag of the water on the blades which tends to close them or keep them in their closed state, with the result that the blades open fully.

FIGS. 2, 2(a), 3 and 3(a) illustrate what will happen if the use of the propeller is no longer required and the engine driving it is therefore turned off. More specifically, in turning off the motor and thereby reducing the centrifugal forces to zero, the drag or force of the water against the blades as the boat moves through the water then becomes dominant to force the blades to turn on bolt 12 and toward each other, as is shown in FIG. 2 wherein the blades are shown in a midway position between being fully openor fully closed. It should be noted that the ends of ears a and 11a, as well as the base of the abovesaid recess in the end of hub member 13, are rounded or arced to facilitate this pivotal movement of the blades. With the drag of the water continuing to act upon them, the blades continue to move towards each other, like the blades of a scissors, until they are fully closed or shut, FIG. 2(a) providing an end view of the blades when they are already in face-to-face relationship and, therefore, almost in a fully closed position. FIGS. 3 and 3(a) illustrate blades 10 and 11 in their fully closed position and it will be noticed from these figures not only the compactness of the construction but also its streamlined nature. In short, in its fully closed position as shown, the entire propeller mechanism presents the smallest cross-sectional area or, stated differently, the smallest surface area, to the water as the boat moves through the water, with the result that the drag forces which would tend to slow the boat are reduced to a minimum.

If, now, the propeller motor is started up again, the hub member 13 and blades 10 and 11 extending therefrom would begin once again to rotate at a high speed and, when this occurs, the centrifugal forces that act upon the blades are introduced once again. As a consequence and as already mentioned, the blades will separate from each other and, in a short time, will reach a fully-opened position, that is to say, the position shown in FIGS. 1 and 1(a).

The manner in which hub member 13 is linked to or mounted on the shaft that drives it and the manner in which propeller blades 10 and 11 are pivotally mounted on the hub member are shown in much greater detail in FIGS. 4, 4(a) and 4(b) wherein these elements are shown in cross-section. Accordingly, referring now to these figures, hub member 13 is shown to have a cylindrically-shaped drive shaft-receiving opening 14 at its front portion that couples with or opens into a coaxial nut-receiving opening 15 at the intermediate portion of the hub member. However, opening 14 into which the driveshaft is to be inserted is preferably of smaller diameter than opening 15, with the result that a shoulder 16 is created at the interface between these two openings, as intended. A washer element 17 is mounted in opening 15 and up against this shoulder 16. The rear portion of the hub member 13 is formed with a pair of aligned walls 13a and 13b defining a radially open recess 130.

A drive shaft 18, Whose tip 18a is threaded, is mounted in opening 14 with its tip 18a extending into recess 15. The hub member further includes a U-shaped cap or nut element 20 whose inside surface is likewise threaded so that it can be screwed onto the threaded tip of the driveshaft. When this is done, the base of nut element 20 will abut against shoulder 16, more specifically, against washer 17, with the result that the driveshaft will then be firmly held or locked in position so that it will not move or slide in and out of the hub member. A square hole 20a in the top or head of nut element '20 is provided so that a wrench mechanism may be inserted therein to turn the nut element in one direction or another to either tighten or loosen it. Nut element 24) is itself locked in position by means of a cotter pin 2012 which extends through the walls of hub member 13 as well as through the nut element.

Thus, in assembling the unit, driveshaft 18 is inserted first and then nut element 20 is tightened over it, with cotter pin 20b inserted last to firmly lock these parts together. Finally, to prevent driveshaft 18 [from turning relative to hub member 13 and thereby becoming unscrewed from nut element 20, keyways 21a and 21b are respectively provided along the outside surface of the driveshaft and along the inside surface of opening 14, these keyways being purposely aligned with each other and having a key 21c inserted therein which thereafter prevents any rotational movement of the driveshaft relative to the hub member. As shown in FIGURES 2 and 3, the rear ends of walls 13a and 13b are convex, as indicated at 22.

With respect to propeller blades 10 and 11, the mounting portions of these blades are provided with flat ears 10a and 11a sandwiched between the Walls 13a and 13b of the hubs recess 13c as is shown quite clearly in FIG. 4. As is also shown quite clearly in these figures, the bottoms of ears 10a and 11a are appropriately rounded or arced to prevent their hitting up against the nut element and thereby having their pivotal movement impeded. Mounting ears 10a and 1111, as well as walls 13a and 13b respectively have holes through themwhich are preferably of the same diameter and which are aligned to form a continuous channel into which bolt 12 is inserted to lock the propeller blades in position and thereby prevent their withdrawal from the recess. To prevent the bolt itself from coming out, a pair of cotter pins 12a and 12b are used, the cotter pins respectively passing through the recess walls and the bolt to lock it in place. Hence, the propeller blades are mounted on the hub after the driveshaft is mounted therein, the end portions of the blades first being inserted in the recess, the bolt then being inserted in the channel provided for it, and the entire arrangement finally being locked in with the mounting of the cotter pins. When this is done, the propeller apparatus is ready to be used as previously described.

Although a particular arrangement of the invention has been illustrated above by way of example, it is not intended that the invention be limited thereto. Accordingly, the invention should be considered to include any and all modifications, alterations or equivalent arrangements falling within the scope of the annexed claim.

Having thus described the invention, what is claimed is:

A folding boat propeller, comprising:

an elongated generally cylindrical hub member formed at its rear portion with a pair of aligned walls defining a radially open recess, the front portion of said hub member being formed with a coaxial driveshaftreceiving opening and the intermediate portion of said hub member being formed with a coaxial nutreceiving opening that is contiguous with said recess and said driveshaft-receiving opening, said walls being .formed with a pair of radially aligned bores and the rear surfaces of said walls being convex in shape;

a driveshaft-engaging nut disposed within said nut-receiving opening forwardly of said recess, said nut having a coaxial wrench receiving hole formed at its rear portion;

a cotter key extending between said hub member and said driveshaft-engaging nut;

a pair of propeller blades, each having a mounting portion that includes a flat ear and a radially outwardly extending surface outwardly of said ear, said ears being sandwiched within said recess and said radially outwardly extending surfaces being concavely curved to conform to the shape of the rear ends of said walls, said ears being formed with radially aligned bores aligned with the bores of said walls;

a bolt extending through the bores of said walls and ears and terminating within said walls to pivotally connect said propeller blades to said hub member whereby said blades will automatically pivot outwardly and forwardly to a driving position solely under the influence of centrifugal force when said hub member is rotated, with said blades automatically pivoting rearwardly and inwardly into a folded position solely under the influence of water pressure, with the rear surfaces of said blades closely abutting 5 5 one another and said mounting portions defining a 938,290 10/1909 Thompson 170-160.52 smooth rearward continuation of said hub member; 2,198,475 4/1940 Dorner 170--160.12 and FOREIGN PATENTS a pair of cotter pins extending through the sides of said hub member and the end portions of said bolt to 5 87,398 9/1869 Francelock said bolt in place within said recess, with the 4,504 1908 Great Britain. exterior of said propeller when folded presenting a 154,495 19 0 Great Britain. substantially projection-free minimum-drag sur-face 878,852 10/1961 Great tmn. to the water as the boat moves through the water. 51,937 1/ 1940 y- References Cited by the Examiner AM EL V E rim y Examiner.

UNITED STATES PATENTS E. A. POWELL, JR., Assistant Examiner.

725,097 4/1903 Learnard 170-16057 JULIUS E. WEST, Examiner. 

